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MRMI <br /> -e.+ a-'ti — c�,.r .� . _ +.e- <br /> _ a+;, n�:I?:r , � r. '-T .� (.`�� :,E ,o r,'x R <br /> 1 - <br /> 4 <br /> I <br /> ry <br /> A <br /> Delta <br /> Environm, <br /> Consultants,Inc . <br /> 3300 Data drive,Suite 100 <br /> Rancho Cordova.CA 95670 <br /> 9101638.2085 <br /> FAX:9161638.8285 <br /> Vrf�t, <br /> 1^ f <br /> - rt <br /> January 11, 1991 <br /> Ms.Diane Hinson <br /> Department of Environmental Health <br /> San Joaquin County <br /> Stockton,California 95201 <br /> Subject: Quarterly Ground Water Sampling Results <br /> 620 West Charter Way,Stockton,California <br /> Shell WIC No.204-7524-4305 <br /> Pelta Project No.40-88-586 <br /> Dear Ms.Hinson: <br /> Delta E:ivironmental Consultants, Inc., has been authorized by Shell Oil Company to conduct au <br /> investigation of soil and ground water conditions at a Shell service station located at 620 West Charter <br /> Way, Stockton, California (Figures 1 and 2). The investigation is intended to characterize the <br /> distribution of petroleum constituents in soil and ground water beneath and adjacent to the site, This <br /> letter report summarizes the results of ground water sampling activities performed at the site on <br /> October 24, 1990. Quarterly ground water samples were collected from the nine monitoring wells <br /> identified in Figure?- <br /> Water <br /> igure2.Water Level Depth, Flow Direction,and Hydraulic Gradient <br /> Ground water level measurements were made monthly between July anal October 19W. Figure 3 depicts <br /> the ground water contours during this period. Ground water le%cl measurements made from all <br /> monitoring wells throughout the duration of?his investigation are compiled in Table 1. A plot of this <br /> historical data(Figure 4)shows a continuous decline in water elevations over the past year,dropping; <br /> by approximately 2 to 4 feet in the wells, <br /> Stiblective Analvsls and Ground Water Sampling <br /> A-_u�;ective analysis for a ground water sample collected from each vfell was performed during each <br /> sampling event according to methods described in Enclosure A. Table I lists the depth of free-phase <br /> petroleum product measured in monitoring wells MW-2,MW-3,MW4,and MW-7. Figure 5 depicts <br /> the inferred extent of product beneath the site. In addition to the free-phase product in monitoring <br /> wells MW-2, MW-3, MW-4, and MW-7,a slight sheen was observed in monitoring wells MW-5 and <br /> MW-8 during Or:ober 1990. These sheens were not observed in subsequent monitoring. <br /> i <br />